1. Field of the Invention
The present invention relates to a portable telephone apparatus provided with a battery alarm function of detecting the voltage level of a battery apparatus and issuing a predetermined battery alarm when a voltage remaining amount drops.
2. Description of the Related Art
A portable telephone apparatus such as a portable cellular phone or a PHS (Personal Handyphone System) terminal uses a battery apparatus provided in an apparatus body as a driving power supply.
Generally, a battery apparatus of a portable telephone apparatus of the type mentioned can be charged to a fixed voltage by means of a charger or the like, and every time the voltage of the battery apparatus drops through use of the telephone apparatus, the battery apparatus is charged to allow the telephone apparatus to be used repetitively.
Usually, a detection element for detecting the voltage level of a battery apparatus is provided in a body or some other element of a telephone apparatus, and if the voltage drops to a predetermined level through use of the telephone apparatus, then a predetermined battery alarm is issued.
Consequently, the user can perform a charging operation before the voltage of the battery apparatus drops fully to zero and therefore can use the portable telephone apparatus continually without any trouble.
A portable telephone apparatus provided with detection and alarm means for a battery apparatus of the type mentioned is disclosed, for example, in Japanese Patent Laid-Open No. 265866/1992 entitled “Battery Voltage Drop Alarming Method”.
In recent years, increase of functions and applications of a portable telephone apparatus has been and is proceeding quickly. Particularly recently, a portable telephone apparatus is provided with, in addition to a talking function with an external apparatus which is an original function of a telephone set (and a displaying function, a voice function, and a setting inputting function necessary for the talking function), various additional functions which have not been provided for conventional portable telephone apparatus such as, for example, a transmission/reception function of an electronic mail, a connection function to the Internet, a game function and a music playback function.
Such increase of functions of a portable telephone apparatus and diversification of additional functions involved therein tend to increase, and it is estimated that further various additional functions are provided in future.
Such various additional functions as mentioned above sometimes require high driving power when compared with the talking function which is an original function of a portable telephone set, and frequent use of such additional functions drops the voltage of the battery apparatus suddenly.
In such a case, in a conventional portable telephone apparatus, an alarm is issued from a battery voltage detection section at a point of time when the voltage of the battery apparatus drops to the lowest voltage level with which the talking function is possible.
Accordingly, if use of an additional function is stopped immediately at a point of time when an alarm is issued and then the battery apparatus is charged, then it is possible to assure the lowest operation voltage with which the talking function operates before the battery apparatus is charged up.
Actually, however, it is sometimes difficult to immediately stop use of an additional function after issuance of a battery alarm.
Further, even if an alarm is issued, the user sometimes discriminates that the battery voltage is still sufficient and therefore continues the use of an additional function.
Therefore, particularly a recent portable telephone apparatus which incorporates various additional functions of high performances has a problem in that, before the user becomes aware, the battery voltage drops until use of the original talking function (origination/termination functions) of a telephone set is disabled before the battery apparatus is charged.
Japanese Patent Laid-Open No. 265866/1992 mentioned above discloses a method of setting an estimation time until the voltage of a battery apparatus drops to the lowest operation voltage level and issuing an alarm.
According to the method, however, a dropping timing to the lowest operation voltage for the original talking function of a telephone set is estimated similarly to the conventional alarm function. Thus, the method cannot be applied well to a portable telephone apparatus of the multi-function type which involves two or more voltages of different lowest operation levels for the talking function and additional functions and with which supervision of a high operation voltage necessary for the additional functions is required.